Binary digital-to-analogue converters



g- 6,1963 I N.C.BEHRINGER ETAL 3,396,383

BINARY DIGITAL-TO-ANALOGUE CONVERTERS Filed Feb. 23, 1965 COUNT-ER 53INVENTORS m g; NORMAN c. BEHRl/VGER BgON/IL R. TREFFE/SEN ATTORNEYUnited States Pat t BINARY DIGITAL-TO-ANALOGUE CONVERTERS Norman C.Behringer, Scottsdale, Ariz., and Donal R.

Trelfeisen, Huntington Station, N.Y., assignors to Sperry RandCorporation, Great Neck, N.Y., a corporation of Delaware Filed Feb. 23,1965, Ser. No. 434,537 8 Claims. (Cl. 340-347) ABSTRACT OF THEDISCLOSURE A binary-to-digital converter having pairs of rotatable codedwheels. Binary ZERO and binary ONE digits of the received signal aresegregated and applied to the first and second wheels, respectively, ofa given pair. The wheels are coded to block successively, each possiblecombination of binary digits and rotated until complete signal blockageoccurs.

This invention relates to digital coded converters and more particularlyto means for converting binary digital signals to their decimalequivalents.

It is frequently necessary to convert binary coded signals used indigital computers to the equivalent decimal coded indication so that theresults of a computation can be readily interpreted by the operator.

Prior art methods for accomplishing this conversion usually requirecomplex mathematical manipulations in that these methods involverepeated operations using relatively elaborate equipment.

Many prior art methods are also subject to errors in conversion in thatthey employ electrical components whose critical characteristics changewith time. These devices are particularly difficult to use in situationsin which incoming data is to be sampled at a low rate.

It is an object of the invention to provide a binary-todecimal converterthat is relatively simple and compact.

It is another object of the present invention to provide abinary-to-decimal converter that operates without conversion error.

It is still another object of the present invention to provide abinary-to-decimal converter that is especially suited for situations inwhich discrete input data signals are presented at a low sampling rate.

These and other objects are accomplished by providing a device in whichselected terminals on a multiple switching means may be energized in apattern representative of the binary signal to be processed, openingvarious circuit combinations in the switching means in a predeterminedsequence, and counting the number of switching functions necessary toprevent all current flow through the switching means.

The principles of the invention may be understood by referring to thefollowing description and the accompanying drawing in which the singlefigure, partly in schematic form, represents one embodiment of theinvention.

Referring now to the figure, a group of input terminals 11 are arrangedto receive individual signals representing the bits of a parallel binarycode. The embodiment shown in the drawing is adapted to receive an 8-bitbinary code.

Signals from the various input lines are conducted to the coils on thevarious double-throw relays 13, 15, 17, 19, 21, 23, 25, and 27. Theserelays are so arranged that a binary ONE on an input line will pull thearmature of the associated relay into the upper or binary ONE position.The armatures of all relays are connected to a power source 29.

A first pair of code wheels 31 and 33 are mounted integrally on a shaft35. These wheels are constructed ac- Patented Aug 6, 1968 cording towell-known techniques so as to have a number of annular tracks.Alternate segments of conductiveand nonconductive material in each trackare arranged to provide a switching sequence in which the successivevalues in the binary code contact the groups of input brushes 37 and 39.The shaded segments in the drawing represent conducting sections whereasthe unshaded segments represent insulating sections.

A central hub of conductive material 41 is electrically connected to allof the conductive segments in a given wheel. Thus an electrical voltageapplied to any one of the conducting segments through an input brush inthe group 37 will enable a current to pass through the wheel 31 and outof the common brush 43. Similarly, the remaining code wheels eachcontain central conducting hubs from which current may be talten by oneof the common brushes 43 and applied to a common bus 44. The innermostannular track 45 contains a single conducting segment and a singleinsulating segment; each succeeding annular track contains double thenumber of segments contained in the next innermost track.

The wheel 31 represents a binary ONE code wheel and is connected to thebinary ONE terminals of the relays 13-19 through the binary ONE inputbrushes 37.

Similarly, the wheel 33 of the first pair represents a binary ZERO codewheel since it is connected to the binary ZERO terminals of the relays13-19 through the binary ZERO input brushes 39. The wheels 31 and 33 areinversely related in that corresponding segments of the two wheels areof the opposite conductivity type. Thus insulating segment 47 of thewheel 33 corresponds to conducting segment 49 of the wheel 31. Bothwheels, however, contain the conducting central hub 41.

A second pair of code wheels 51 and 53 are mounted integrally on a shaft55. The wheel 51 is identical to the wheel 31 and the wheel 53 isidentical to the wheel 33. Wheels 51 and 53 are driven directly from anelectric motor 57 through the shaft 55.

A second shaft 59 is driven by the motor through the bevel gears 61. Theshaft 59 drives a 16:1 speed reducer 63 which, in turn, drives the shaft35 through the bevel gears 65.

It should be noticed that the first pair of wheels 31 and 33 alwaysretain the same spatial relationship with respect to eachother sincethese wheels are mounted on the same shaft. In the same fashion, thesecond pair of wheels 51 and 53 always retain the same spatialrelationship with respect to each other. The spatial relationshipbetween the first and the second pairs is not fixed, however, butchanges during an operating cycle because of the speed reducer 63.

The annular tracks of the code wheel 51 are connected through individualbrushes to the upper or binary ONE terminals of the lower order relays21-27. The annular tracks of the code wheel 53 are connected throughindividual brushes to the lower or binar-y ZERO terminals of the samerelays.

Thus the first pair of code wheels 31 and 33 respond to the higher ordervalues in the received binary coded signals whereas the second pair ofcode wheels 51 and 53 respond to the lower order values in the receivedbinary coded signals.

The input brushes operate as scanning elements in that they traverse thevarious combinations of segments dur ing an operating cycle. Althoughthese electrical conduction and non-conduction combinations that havebeen described are presently preferred, it will be appreciated thatother scanning methods may be employed. Photoelectric scanning elements,for instance, combined with code wheels containing opaque andtransparent segments might be preferred in certain applications. In thisarrangement, the passage of light through any transparentsegrneptlwouldjbe used to generate an electrical signal that 7 could beamplified and applied to the motor and brake.

An electrically operated brake 67 is connected in paralleLWith the motor57. The brake operates to clamp the shaft 55 whenever power flow to thebrake is interrupted. This brake serves to prevent overtravel when themotor is turned off. I A decimal counter 69 is actuated through theshaft 55. This counter is arranged to advance one unit each timethebrush on the outermost annular track of the wheel 51 passes from onesegment to the next. A counter in the form of a drum display, arrangedto provide, 16 counts for each revolution of the shaft 55 is presentlypreferred, however, other Well-known types of displays such asphotoelectric shaft sector counters may be used if desired.

The counter in general, should have a capacity equal to the capacity ofthe code wheels. Thus for the con verter illustrated in the accompanyingfigure, a counter would preferably have a capacity of 256 so thatresetting the code wheels to a position of zero reading would also resetthe counter. However, counters having an independent reset means may beused for this purpose if desired.

When a parallel binary signal is applied to the group of input lines 11,the relays connected in those lines receiving a binary ONE will beactuated thus establishing a current path from the power source to theappropriate binary ONE code wheel 31 or 51 as the case may be. Relaysthat are connected to a line receiving a binary ZERO signal will remainunactuated thus retaining a current path from the power source 29 to thebinary ZERO code wheel 33 or 53 as the case may be. Any input brush thusenergized that happens to be in contact with a conducting segment willallow a current to pass through the output brush so as to release thebrake 67 and energize the motor 57. Current flow to the motor willcontinue until each wheel reaches the position in which each energizedinput brush contacts an insulating segment.

To begin an operating cycle, the code wheels and the counter are set toa zero position. In the zero position, none of the relays are energized,therefore none of the input brushes associated with the binary ONE codewheels 31 and 51 are energized. All of the input brushes connected tothe binary ZERO input wheels 33 and 53, however, are energized. Theposition of the code wheels corresponding to a given binary number isthat position in which each input brush that happens to be energizedcontacts an insulating segment. For the zero position of the codewheels, this will occur when the wheel 33 is rotated to the position inwhich the segment 47 contacts the outermost brush of the group 39 andthe wheel 53 is rotated to the position in which the segment 71 contactsthe outermost brush associated with that wheel. This, of course, willbring the segment 49 on wheel 31 into contact with the outermost brushof group 37 and a segment 73 on the wheel 51 into contact with theoutermost brush associated with that wheel. These binary ONE brushes,however, are not energized, therefore current cannot flow through theseparticular paths even though the brushes happen to contact conductingsegments.

With the wheels in the position indicated, no current can flow to themotor 57 and the brake 67 will clamp the shaft 55 in the properposition.

If, now, a binary ONE (00000001) is applied to the input lines, the 2line will be energized. The relay 27 will pull in so that current canflow through the outermost brush on the wheel 51, through the segment 73to the brush 43 and on to the motor 57 and the brake 67. This willrelease the brake and cause the motor to rotate the shaft 55counterclockwise until the code wheel 51 reaches the next segment. Thisnext segment is an insulating segment so current flow through thisoutermost brush is interrupted. Current flow cannot be establishedthrough any of the remaining binary ONE input brushes because none ofthese are energized. Current flow cannot be established through theenergized binary ZERO input brushes because they contact insulatingsegments on the wheel 53.

Since the code wheels 31 and 33 turn at the speed of the code wheels 51and 53, the various segments originally in contact with the inputbrushes of the slower moving wheels 31 and 33 will remain in contactduring this conversion cycle.

In orderto better visualize the operation of the circuit when largernumbers are encountered, assume that the binary equivalent of the number83 is encountered. In binary form, this number is equal to 0101001]. Therelays will be set in the condition shown in the drawing and the codewheels will ultimately come to rest in the position shown in thedrawing.

At the beginning of the cycle the wheels are set to the zero position.This is the position in which the segments 47, 49, 71, and 73 are incontact with their respective brushes.

During the first revolution of the wheels 51 and 53, the outermost brushof the wheel 31, which is energized, will provide a current path to themotor and brake regardless of the condition of the remaining brushes.During the second revolution of the wheels 51 and 53, the outermostbrush of the wheel 31 will be in contact with an insulating segment 77,however the neXt-to-innermost brush on the same wheel is energizedthrough the relay 15 and is in contact with the conducting segment 79.By following the operation in this manner it will be seen that at leastone energized brush associated with the wheels 31 and 33 is in contactwith a conducting segment for five complete revolutions of the wheels 51and 53. At the beginning of the sixth revolution of these wheels, thecounter will have a reading of and the wheels 31 and 33 will be in aposition such that the outermost brushes are just making contact withthe segments with which they are shown in contact in the drawing. Inthis position, no current paths are available to conduct current to themotor and the brake through these particular Wheels. Any current fiowingto the motor must be received through the wheels 51 and 53. Currentpaths will be established through these wheels until an additional threesegments have contacted brushes associated with the wheels 51 and 53'andthey are in the position depgcted. The counter will now display adecimal count of K 3.!)

Although the speed reducer has been illustrated as having a ratio equalto 16:1, it will be understood that this ratio depends upon theparticular design of the code wheels. The reducer must rotate the slowermoving wheels at a speed such that they advance one segment for eachrotation of the faster moving wheels. In general, for the type ofconverter shown in the drawing, the slower moving whee-ls should rotateat a speed equal to 2- times the speed of the faster moving wheels whena 211' bit code is to be used.

A device constructed according to the principles of the presentinvention is essentially a mechanically actuated switching device inwhich the inverse code wheels provide positive control. Such a device isnot dependent upon critical amplifiers or other electronic componentsthat may drift and cause conversion errors.

Because the code wheels are rotated only during an actual conversionoperation, the device is ideally suited for situations involving lowdata sampling rates.

It will be appreciated that the principles of the invention can beapplied to circuits in which more than two pairs of code wheels areemployed or to circuits using only a single pair of code wheels. Codewheels having more than four tracks may also be employed in order toaccommodate binary codes having more than four hits.

If desired, the two code Wheels constituting a single pair may becombined in a single wheel. In this instance the single wheel could, forinstance, contain the tracks corresponding to the binary ONE wheel nearthe central portion of the single wheel and the tracks corresponding tothe binary ZERO wheel near the rim of the single wheel.

In general, any cyclically operated switching means capable ofconnecting various combinations of cur-rent paths representing eithersuccessively greater or successively smaller values of the desired codemay be used in practicing the invention. Photoelectric code whee-ls,code drums, or tapes may be used in preference to the particular codewheels described heretobefore if so desired.

Although a decimal counter is presently preferred as a readout device,it will be appreciated that any one of a wide variety of devices thatare capable of indicating the magnitude of the shaft rotation may beemployed if desired.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of the invention in its broader aspects.

What is claimed is:

1. A binary-to-decimal converter comprising means to receive a binarycoded signal; a group of binary ZERO scanning elements; a group ofbinary ONE scanning elements; means to energize individual binary ZEROscanning elements corresponding to binary ZERO digits in a receivedsignal; means to energize individual binary ONE scanning elementscorresponding to binary ONE digits in the received signal; means coupledto each scanning element to provide a driving current when any scanningelement is energized; cyclical switching means to block the flow of anydriving current arising from various selected combinations of scanningelements; driving means to actuate said switching means in the sequencein which successive selected combinations represent successively greaterbinary numbers in the code to be used, said driving means beingenergized by said driving current; and means to count the number ofswitching operations undergone by said switching means.

2. A binary-to-deci-mal converter comprising a group of binary ZEROinput brushes; 2. group of binary ONE input brushes; means to energizethose binary ZERO input brushes corresponding to binary ZERO digits inthe received signal; means to energize those binary ONE input brushescorresponding to binary ONE digits in the received signal; cyclicalswitching means cooperating with each group of input brushes to blockthe flow of current from selected combinations of said brushes; drivingmeans to actuate said switching means in the sequence in whichsuccessive selected combinations represent successively greater binarynumbers in the code to be used, said driving means being energized onlythrough said switching means; and means to count the number of switchingoperations undergone by said switching means.

3. A binary-todeci-mal converter comprising a group of binary ZERO inputbrushes; a group of binary ONE input brushes; means to energize thosebinary ZERO input brushes that correspond to binary ZERO digits in thereceived signal; means to energize those binary ONE input brushes thatcorrespond to binary ONE digits in the received signal; first and secondbinary code wheels cooperating with the binary ZERO and binary ONE inputbrushes respectively, said first and second code wheels being integrallymounted on a common shaft, said code wheels further having inverselyrelated patterns of conducting and nonconducting segments; electricallyactuated means to rotate said wheels; means to energize saidelectrically actuated means from said input brushes through said codewheels; and means to indicate the total rotational motion of said wheelsduring a conversion cycle.

4. A binary-to-decimal converter comprising an individual inputswitching means for each digit in the binary code to be used; first andsecond groups of conductors,

each group having a conductor representative of each digit in the binarycode to be used; said input switching means being arranged to energizethe associated conductor in either one of said first and second groupsaccording to the value of the binary digit received by that switchingmeans; first and second cyclical switching means for sequentiallyconnecting various combinations of current paths to an external circuit,said combinations of current paths being representative of successivevalues in a binary code, said combinations of current paths beingarranged so that a given value in the binary code is represented by acombination which prevents current flow; said first and second groups ofconductors being connected to the input of said first and secondcyclical switching means respectively; electrically operated means toactuate both cyclical switching means in response to currents passingthrough any of the combinations .of current paths; and a decimal counterarranged to count the number of combinations switched by the cyclicalswitching means during an operating cycle.

5. A binary-to-decimal converter comprising a plurality of input leadsequal in number to the number of digits in the binary code to be used;first and second groups of conductors; individual input switching meansconnected to each input lead, said input switching means being arrangedto energize the corresponding conductor in said first group when theassociated input lead receives a binary ONE signal, said input switchingmeans being further arranged to energize the corresponding conductor insaid second group when the associated input lead receives a binary ZEROsignal; first and second cyclical switching means for sequentiallyconnecting various combinations of current paths to an external cirouit,said combinations of current paths being representative of successivevalues in a binary code, said combinations of current paths beingfurther arranged so that a given value in the binary code is representedby a combinatioin which prevents current flow; said first and secondgroups of conductors being connected to the input of said first andsecond cyclical switching means respectively; an electric motor toactuate both of said cyclical switching means, said electric motor beingenergized through said cyclical switching means; and a decimal counterarranged to indicate the total rotation of the shaft of said motor.

6. In combination:

(a) first and second code wheels mounted integrally on a common shaft,

(b) a motor to rotate said shaft,

(c) a brake to arrest the rotation of said shaft,

((1) a counter to indicate the total rotation of said shaft,

(e) a plurality of annular tracks on each code wheel, said tracks beingdivided into alternate conductive and nonconductive segments, saidsegments being proportioned so that the member of segments in any trackis double the number of segments in the next smaller track, theinnermost of said tracks containing a single conductive and a singlenonconductive segment,

(f) the segments on the two wheels being further arranged in an invertedrelationship so that any conductive segment on one wheel is paired witha nonconductive segment in the corresponding position on the otherwheel,

(g) a plurality of signal input lines equal in number to the number oftracks on either of said code wheels,

(h) a double-throw relay for each signal input line,

each of said relays being actuated through the associated signal inputline,

(i) a plurality of brushes, each brush contacting an associated one ofsaid tracks,

(j) means to connect the normally open contacts on the various relays tothe individual brushes associated with the first of said code wheels,

. 7 (k) means to connect the normally closed contactson the variousrelays to the individual brushes associated with the second of said codewheels,

(1) means to connect the 'armatures of all of the relays to a commonsource of potential,

(m) means toconduct an electrical current from the code wheels to saidmotor whenever any of the brushes contact a conducting segment, and

(n) Means to engage said brake whenever the motor is de-energized.

7. A binary-to-decimal converter comprising first and second groups ofbinary ZERO input brushes; first and second groups of binary ONE inputbrushes; means to energize those binary ZERO input brushes thatcorrespond to binary ZERO digits in the received signal; means toenergize those binary ONE input brushes that correspond to binary ONEdigits in the received signal; first and second pairs of binary codeWheels; first and second code Wheels in said first pair cooperating withsaid group of binary ZERO input brushes and with said first group ofbinary ONE input brushes respectively; first and second code Wheels insaid second pair cooperating with said second group of binary ZERO inputbrushes and with said second group of binary ONE input brushesrespectively; said first and second code wheels in each pair furtherhaving inversely related patterns of conducting and nonconductingsegments; electrically actuated means to rotate the first pair of codewheels; a speed reducer to rotate the second pair of code wheels at 4the speed of the first pair of code wheels; means to energize saidelectrically actuated means from said input brushes through any of saidcode wheels; and means to indicate the total rotation of said first pairof code wheels.

8. A binary-to-decimal converter for use with a 2n bit parallel codecomprising:

(a) a first pair of cod-e wheels mounted integrally on a first commonshaft,

(b) a second pair of code wheels mounted integrally on a second commonshaft,

(c) a motor to rotate the first common shaft,

(d) a speed reducer to rotate the second common shaft at a speed equalto 2 times the speed of the first common shaft,

(e) a brake to arrest the rotation of the motor,

(f) n annular tracks on each code wheel, said tracks being divided intoalternate conductive and nonconductive segments, said segments beingproportioned so 8 that the number of segments in any track is double thenumber of segments in the next smallertrack, the innermost of saidtracks containing a single conductive and a single nonconductivesegment,

(g) the segments on the two wheels in a given pair being furtherarranged in an inverted relationship so that any conductive segment onone wheel is paired with a nonconductive segment in the correspondingposition on the other wheel of that pair,

(h) 2w signal input lines,

(i) a double-throw relay for each signal input line, each of said relaysbeing actuated through the associated signal input line,

(j) a plurality of brushes, each brush contacting an associated one ofsaid tracks,

(k) means to connect the normally open contacts on the various relays tothe individual brushes associated with the first of said code wheels ineach pair,

(1) means to connect the normally closed contacts on the various relaysto the individual brushes associated with the second of said codewheeels in each pair,

(in) means to connect the armature of all of the relays to a commonsource of potential,

(it) means to conduct an electrical current from the code wheels to saidmotor whenever anyone of the brushes contact a conducting segment, and

(0) means to engage said brake Whenever the motor is de-energized.

References Cited UNITED STATES PATENTS Kernahan et al. 318-28 MAYNARD R.WILBUR, Primary Examiner. W. J. KOPACZ, Assistant Examiner.

